Method for making a flexographic printing plate from a flexographic printing element having a powder layer

Abstract

A photosensitive printing element having an overall layer of powder material and a process for making a flexographic printing plate from such an element are disclosed. The photosensitive element includes a support, a photopolymerizable layer, and a layer of powder material on the photopolymerizable layer. The layer of powder material can be opaque or transparent depending upon desired use.

What is claimed is: 
     
       1. A method for making a flexographic printing plate from a photosensitive element which comprises: (a) a support shaped into a hollow cylinder;   (b) at least one seamless photopolymerizable layer on an exterior surface of the support comprising an elastomeric binder, at least one monomer and an initiator, an entire exterior surface of the photopolymerizable layer opposite the support being tacky or substantially tacky, said cylindrical support and seamless photopolymerizable layer being expandable and contractible; and   (c) a non-film layer of particulate powder material on the exterior surface of the photopolymerizable layer, wherein the powder layer is opaque and insensitive to actinic radiation and renders the surface tack-free, comprising (1) imagewise removing areas of the powder layer from the cylindrical element, to create an in-situ cylindrical mask;   (2) overall exposing the photopolymerizable layer through the cylindrical mask with actinic radiation to form an imagewise exposed element;   (3) treating the element of step (2) with a solution to remove the areas of the photopolymerizable layer which were not exposed to actinic radiation and the areas of the mask not removed in step (1).     
     
     
       2. The method of claim 1 further comprising prior to the treating step, backflash exposing the element overall to actinic radiation through the support. 
     
     
       3. The method of claim 1, further comprising a post-exposure step after the treating step. 
     
     
       4. The method of claim 1, further comprising a detackification treatment after the treating step. 
     
     
       5. The method of claim 4 wherein the detackification treatment comprises exposure to light having a wavelength less than 300 nm. 
     
     
       6. The method of claim 1 wherein the imagewise removing is by laser radiation. 
     
     
       7. The method of claim 6 wherein the laser radiation is 750 nm to 1060 nm and the powder absorbs infrared radiation. 
     
     
       8. The method of claim 7 wherein the powder is black and the laser radiation is 1060 nm.